13.7%-efficient Zn(Se,OH)(x)/Cu(In,Ga)(S,Se)(2) thin-film solar cell

Cu(In,Ga)Se-2 (CIGS) and related semiconducting compounds have demonstrated their high potential for high-efficiency thin-film solar cells. The highes t efficiency for CIGS-based thin-film solar cells has been achieved with Cd S buffer layers prepared by a solution growth method known as chemical bath deposition (CBD). With the aim of developing Cd-free chalcopyrite-based th in-film solar cells, Zn(Se,OH)(x) buffer layers were deposited by CBD on po lycrystalline Cu(In,Ga) (S,Se)(2) (CIGSS). A total-area conversion efficien cy of 13.7% was certified by the Frauenhofer Institute for Solar Energy Sys tems. The CIGSS absorber was fabricated by Siemens Salar Industries (Califo rnia). For device optimization, the thickness and good surface coverage wer e controlled by XPS-UPS photoemission spectroscopy. A Zn(Se,OH)(x) thicknes s below 7 nm has been found to be optimum for achieving a homogeneous and c ompact buffer film on CIGSS, with open-circuit photovoltage V-oc = 535 mV, fill factor FF = 70.76% and a high short-circuit photocurrent density J(sc) = 36.1 mA cm(-2). (C) 1998 John Wiley & Sons, Ltd.